Antiknock compositions



. scavengers present in the fuel charge United States Patent 3,074,788 ANT IKNOCK COMPOSITIONS Edmund L. Niedzielski, Graylyn Crest, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Apr. 5, 1960, Ser. No. 19,992 16 Claims. (Cl. 4469) This invention relates to antiknock compositions and more particularly to compositions of organolead antiknock compounds and novel combinations of halohydrocarbon scavenging agents for the lead.

organolead antiknock compositions are widely used to improve octane ratings of fuels for high compression Otto cycle engines. These compositions consist essentially of the organolead antiknock agent and at least one halohydrocarbon that is a scavenger for lead in the combustion process,that is, is able eventually to convert the lead content of the organolead into relatively volatile lead halides. In the absence of halohydrocarbon scavenger, build up of lead-containing deposits soon becomes excessive for smooth functioning of the engines. Even with efiicient undergoing combustion, deposits gradually accumulate. Such accumulation is particularly troublesome in high compression engines such as those of present day passenger cars and trucks, especially under the conditions of low speed and light load exemplified by city driving. The deposits ultimately cause or lead to (1) increased octane requirement of the engine, (2) premature ignition of the fuel charge, (3) spark plug fouling, and (4) malfunctioning as well as decreased life of the exhaust valves.

This invention is directed primarily to alleviating the difficulties associated with malfunctions resulting from the accumulation of deposits on and corrosion (burning) of the exhaust valves. For example, high spots (accumulated deposits) and low spots (actual loss of metal by corrosion) on the face and seat of an exhaust valve prevent proper positioning (closing) of the valve. The result is valve leakage, indicated by undue variations in compression pressures, and consequentially poor engine performance. Valve burning is the more severe condition, dependent more on the corrosive nature of the exhaust gases and deposits than on the amount of the deposits. The corrosivity of these substances appears in some way related to the composition of the antiknock additive conventionally defined in terms of the theories of halogen as halohydrocarbon per atom of lead as organolead, one theory of halogen being that quantity of halohydrocarbon stoichiometrically required to convert all the lead of the organolead to lead dihalide. However, present knowledge provides insufficient basis for predicting the effects of different lead scavenging compositions on exhaust valve performance.

R. H. Blaker in US. Patent 2,784,160 discloses that certain fluorine-containing halohydrocarbons, including 1,1,2,2,-tetrachloro-1,Z-difluoroethane, are effective to overcome some of the adverse effects of deposits in Otto cycle engine operations, when present in the combustion chamber in amounts corresponding to from about 0.1% to about 2% by weight of the hydrocarbon fuel. They decrease the equilibrium octane requirement of the engine and also usually decrease the amounts of deposits in the 3,074,788 Patented Jan. 22, 1963 combustion chamber. The minimum amount of 0.1% of 1,1,2,2-tetrachloro-1,2-difluoroethane, based on the weight of the gasoline, corresponds to 2.6 theories of total halogen based on 3 ml. of tetraethyllead per gallon of fuel. Blaker employed a 100 hour test in a single cylinder Lauson engine and reported that the induction system and valves were clean with no evidence of valve burning. However, it has now been found that, when such amounts of l,l,2,2-tetracliloro-l,Z-difluoroethane are used in fuel employed in multiple cylinder engines, particularly over longer periods of time, objectionable burning on at least some of the valves frequently occurs, as shown particularly by changes in compression pressure. Usually, visual inspection alone cannot adequately detect valve burning even after exposure times of 200-300 hours, but changes in compression pressure can be relied upon to give indications of valve burning under proper test conditions.

It is an object of this invention to provide novel organolead antiknock blends. Another object is to provide organolead antiknock blends containing a mixture of halohydrocarbon scavenging agents which materially decrease the burning of exhaust valves and other difliculties that tend to arise in the use of organolead antiknock compositions containing halohydrocarbon scavenging agents in fuels for Otto cycle engines. A particular object is to provide tetrahydrocarbonlead antiknock blends containing 1,1,2,2-tetrachloro-l,Z-difluoroethane and other halohydrocarbon scavenging agents which overcome the disadvantages and difficulties heretofore encountered in the use of 1,1,2,2-tetrachloro-1,2-difluoroethane as a scavenging agent. A further object is to provide antiknock compositions of the aforesaid character which, as additives in hydrocarbon fuels for Otto cycle engines, are effective to improve exhaust valve performance as well as to control the accumulation and character of combustion chamber deposits. Another object is to provide new fuel compositions comprised essentially of hydrocarbon fuels for Otto cycle engines and the aforesaid antiknock compositions. Still other objects are to provide new compositions of matter and to advance the art.

The above and other objects may be accomplished in accord with this invention which includes tetrahydrocarbonlead antiknock blends comprised essentially of a tetrahydrocarbonlead antiknock compound and a mixture of halohydrocarbon scavenging agents providing 0.1 to about 0.33 theory of fluorine, 0.3 to about 0.5 theory of bromine, and sufficient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of 1,l,2,2,-tetrachloro-l,2- difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one halohydrocarbon in which each halogen has an atomic weight between 35 and in an amount to provide all of said bromine and the rest of said chlorine; and fuels for Otto cycle engines comprised essentially of hydrocarbon fuels in the gasoline boiling range containing said antilcnock compositions in an amount to provide 0.5 to 4 ml. of the tetrahydrocarbonlead antiknock compound per gallon of fuel.

It has been found that the tetrahydrocarbonlead antiknock blends of this invention, when so used in fuels for Otto cycle engines, lead to significant improvements in exhaust valve performance while efficiently scavenging lead during the operation of the engine, decreasing the a, vegan ill equilibrium octane requirement of the engine, and decreasing the amount and altering the character of deposits in the combustion chamber. When the antiknock com positions of this invention are employed in the hydrocarbon fuels in an amount to provide 4 ml. of tetrahydrocarbonlead per gallon of fuel, the concentration of the l,1,2,2-tetrachloro-l,Z-difluoroethane based on the total fuel composition will be less than 0.055% by weight. The improved Valve performance shows up during extensive engine operation as less valve leakage, narrower fluctuations in compression pressure from one cylinder to another of multicylinder engines, and less valve burning. The overall effects are smoother multicylinder operation and longer valve life. The high scavenging efficiency provided by the combination of halohydrocarbon scavenging agents of this invention is indicated by lessened tendencies of an engine to show increase in its octane number requirement on prolonged operation. On the other hand, the novel compositions of this invention do not exert a significant deleterious effect on the performance of the fuel or on other aspects of engine operation.

The tetrahydrocarbonlead antiknock compounds may be any of those which are known to the art as antiknock agents for hydrocarbon fuels for Otto cycle engines. The hydrocarbon radicals in the tetrahydrocarbon lead may be alkyl or aryl, such as methyl, ethyl, propyl, butyl and phenyl. Usually, the antiknock compound will be a lower tetraalkyllead in which the akyl groups are methyl or ethyl, such as tetraethyllead, tetramethyllead, dimedlyldiethyllead, methyltriethyllead, trimethylethyllead, and mixtures of any two or more thereof. Preferably, the antiknock agent will be tetraethyllead, which is readily available commercially, or a mixture thereof with tetramethyllead.

The 1,1,2,2-tetrachloro-1,Z-difiuoroethane may be used in a proportion to provide as little as 0.1 theory of fluorine and 0.2 theory of chlorine and as much as about 0.33 theory of fluorine and about 0.67 theory of chlorine. Preferably, it will be employed in a proportion to pro vide at least 0.2 theory of fluorine and 0.4 theory of chlorine and, most preferably, to provide about 0.33 theory of fluorine and about 0.67 theory of chlorine. The term theory of halogen is a conventional term commonly employed in this art to define the amount of halogen as halohydrocarbon per atom of lead present in the tetrahydrocarbonlead antiknock compound, one theory of halogen being that quantity which is stoichiometrically required t convert all of the lead of the tetrahydrocarbonlead to lead dihalide, i.e. 2 atoms of halogen for each atom of lead in the composition.

In addition to the 1,1,2,2-tetrachloro-1,2-difluoroethane, it is essential that the antiknock composition or the fuel contain at least 0.3 theory of bromine in the form of a halohydrocarbon in which each halogen has an atomic Weight between 35 and 80. Omission of the bromine entirely or reducing it materially below 0.3 theory, tends to result in the opposite and harmful eifect of valve leakage due to valve burning. Usually and preferably, the compositions of this invention will contain such halohydrocarbon in an amount to provide about 0.5 theory of bromine.

The compositions of this invention should contain a total of 1 to about 2 theories of halogen, fluorine plus bromine plus chlorine. When the amounts of 1,l,2,2- tetrachloro-l,2-difluoroethane and bromohydrocarbon are insufficient to provide the desired amount of halogen, a chlorine-containing halohydrocarbon should be included to provide the additional amount of halogen required.

The halohydrocarbon scavenging agents in which each halogen has an atomic weight between 35 and 80, i.e. is bromine or chlorine, are well known to those skilled in the art. Preferably, such halohydrocarbon scavenging agents will be the conventional ethylene dihalides such as ethylene dibromide, ethylene dichloride, and 1-brorno-2- chloroethane. However, other halohydrocarbons of the broad class may be employed, such as mixed dibrornotoluenes, dichlorotoluenes, brornochlorotoluenes, propylene trichloride, propylene tribromide, and like bromohydrocarbons, chloro-hydrocarbons and bromochlorohydrocarbons. Preferably, a mixture of ethylene dibromide and l,1,2,2-tetrachloro-LZ-diiluoroethane will be employed to provide the required theorie of fluorine, bromine and chlorine.

As is conventional in this art, the tetrahydrocarbonlead antiknock blends of this invention usually will contain a small proportion of an identifying dye and a minor proportion of an inert solvent oil, usually kerosene, and may also contain stabilizers, metal deactivators, and the like.

The combination of tetrahydrocarbonlead and mixture of haiohydrocarbon scavenging agents of this invention will be employed in the conventional fuels for Otto cycle engines which essentially are hydrocarbon fuels in the gasoline boiling range, including cracked gasolines and synthetic fuels composed of a single hydrocarbon or a mixture of hydrocarbons in said boiling range. Such fuels may also contain identifying dyes, antioxidants, metal deactivators, anti-icing agents and other functional additives normally associated with finished commercial motor fuels.

Such motor fuels will-contain the tetrahydrocarbonlead antiknock compound in a proportion of from 0.5 to 4 ml. per gallon of fuel and the corresponding proportions of the halohydrocarbon scavenging agents. When so used, the concentration of the l,l,2,2-tetrachloro-l,2- dilluoroethane will be less than 0.055% by weight based on the total fuel composition. Usually, it will be desired to employ the l,1,2,2-tetrachloro-1,2-difluoroethane in a concentration of at least 0.01% by weight of the fuel composition. Absolute concentrations of the 1,1,2,2- tetrachloro-l,2-diflu0roethane materially greater than 0.055% by weight of the fuel composition tend to promote valve burning. Further improvements are obtained by employing (along with the tetrahydrocarbonlead antiknock compound, the 1,1,2,2-tetrachloro-l,Z-difluoroethane and the other halohydrocarbon scavenging agents) an organophosphorus compound to minimize preignition tendencies of the engine and to reduced spark plug fouling, such organophosphorus compounds being well known in the art.

The fluoro-chloro-ethane may be employed as a blend with the other ingredients or it may be added separately or in combination with any one or more of the other ingredients, as described by Blaker in U.S. Patent 2,784,160; provided of course it is present in the combustion chamber in the proportions and amounts given above at the time the fuel charge is ignited. Preferably, it will be employed along with the other ingredients as a blend, e.g. as a tetraethyllead antiknock composition.

Some typical antiknock compositions are illustrated below, wherein TEL stands for tetraethyllead. The quantities are in parts by weight. The compositions are prepared by mixing the ingredients (in any order) to produce homogeneous blends.

Examples: Antz'knock Compositions Examples: Antiknock Compositions-Continued 4.95 0.78 0.75 (0.50 C1+0.25 F) 1. 44 0. Br 0. 76 0. 5 Cl Example 4:

1 011000121? 0.31 0.3 (0.2 Cl+0.1 F) BICHzCHzBL 1. 44 O. 5 B! ClCHzCH Cl 1. 52 1.0 01

Example 5:

TEL 4. 95 FClgOCChF 1.04 1.0 (0.67 Ol+0.33 F) BICHqOHgBI 1. 44 O. 5 Br Tolyl diphenyl phosphate- 0. 69 0. 2 P 1 Example 6:

TEL; 4. 95 FClzCCCl2F 0.31 0.3 (0.2 Cl+0.1 F) BrCHgCH1Br 0. 87 0.3 Br CIOHQOHIC'I 0. 61 0. 4

1 The total weight of the composition when added in grams to each gallon of a gasoline rovides 3 ml. or TEL (tetreethyllead) per gallon. It should be noted a so that 1.04 grams of FClzCCClrF per gallon of gasoline corresponds to about 0.04% by weight.

2 Theories of P are based on the stoichiometry of converting Pb of TEL to Pb: (P04);

Valve Performance: Methods and Examples During the operation of an engine, the compression etc, and, as a result, show greater or lesser tendencies to accumulate deposits in the valve area and to suffer corrosive attack with consequent pressure leakage.

In the tests described below, a late model 10:1 compression ratio V-8 engine was operated on a given fuel 200 hours under the following cyclic conditions: 3.3 minutes at 2000 rpm. and 25 brake horse power, deceleration under load to idle, 1 minute idle at 700 r.p.m. and acceleration under load with one of 4 accelerations at wide open throttle and 3 at part throttle. The base fuel in each test was the same blended gasoline, an article of commerce, to which was added an antiknock composition consisting of tetraethyllead (TEL) in quantity suflicient to give a concentration of 3 m1. of tetraethyllead per gallon and other ingredients as specified below. The lubricant was a standard crankcase lubricating oil composition which, like the base fuel, was not critical for the invention.

The effects of antiknock compositions on exhaust valves (performance and condition) were determined by (a) visual inspection of the valves (seats and faces) for deposits, signs of burning, and degree of seating, and (b) measurements of the compression pressure of each cylinder before and after the engine test.

The compression pressure of a cylinder was the maximum pressure attained, using the CPR compression gage, by cranking the engine over a minimum of :10 revolutions. All measurements were related to a fixed cranking speed of 180 r.p.rn., the correction being a change in p.s.i. of 1 for a change in r.p.m. of 5.

The examples below show that the range in A compression' pressure and the extent of exhaust valve leakage is minimal when the engine is operated on a fuel composition according to the invention.

Changes in Cylinder Compression Pressure and Octane Requirement A Compression Pressure at 180 r.p.m., p.s.i. in Equil.

Test Scavenger, Theories 1 Cylinder N0. Octane Requirement 1 2 3 4 5 6 7 8 Range Non 4 16 13 17 19 ll 11 14 15 0.5 Br+1.0 Cl 10 10 11 13 9 16 2 15 18 98. 3 0.5 Br+1.0 Cl-l-2.6 FClzCCClzF 7 27 7 12 2 15 3 72 1.5 FClzOCC F 41 4 6 13 3 18 0 1 59 98. 8 0.5 Br+1.0 FClzCCClzF 12 11 9 14 11 10 14 14 5 97. 0 0.5 Br+1.0 FChOOClzF-l-Ofl P 22 23 19 18 21 19 19 22 5 1 Br as ethylene dibromine; 01 as ethylene dichloride; P as tolyl diphenyl phosphate; 1.0 FClzCCClrF is equal to 0.67 Cl+0.33 F.

understood that not all valves need be fouled or burned to the same extent. Why one burns and another not appears inherent in the design of the engine, for example, in the design pattern of the fuel intake and distribution system. It is well known that, in a V-8 engine for example, the distribution of the fuel charge may vary from 'one bank to the other, and from one cylinder to another in each bank. The composition of the fuel charge, with regard to fuel/air ratio, antiknock concentration, scavenger concentration, and light and heavy fuel ends, tends to vary from one part of the engine to another. Thus, some cylinders may on the average be running on richer orleaner charges than others or may be receiving somewhat different proportions of the scavenging composition,

Tests 5 and 6 illustrate use of novel compositions of this invention. Tests 1-4 are for comparison only.

Test'2 shows the typical behavior of exhaust valves when the conventional tetraethyllead automotive mix is .present in the gasoline.

' In test 3, 2.6 theories of FCl CCCl F is equivalent to 0.1% by weight of the gasoline; this test was stopped after 137 hours. The exhaust valve of the No. 2 cylinder was severely burned, as indicated by the 45 p.s.i. change in compression pressure and confirmed on visual examination.

Test No. 4 likewise shows valve burning (No. 1 valve) and relatively poor performance of valves Nos. 2, 5, 7 and The relatively small change in compression pressures in tests 5 and 6 illustrates the smooth valve performance in the presence of the compositions of this invention; there is no significant tendency to valve leakage and burning, confirmed on visual examination of each valves face and seat for deposits and corrosion. Further, test 5 shows a significant -1.3 octane number reduction in the requirement of the engine over the conventional antiknock mix of test 2.

It will be understood that the preceding examples have been given for illustrative purposes solely and that, subject to the limitations set forth in the general description, many variations can be made in the compounds and proportions thereof employed without departing from the spirit or scope of this invention.

From the preceding, it will be apparent that this invention provides novel tetrahydrocarbonlead antiknook blends and fuel compositions for Otto cycle engines which provide new and unobvious results and effectively solve serious problems presented by related compositions and their use. Particularly, it greatly decreases the deleterious efiects of tetrahydrocarbonlead antiknock compositions and the scavengers commonly employed therewith on the valves of Otto cycle engines. Therefore, it will be apparent that this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A tetrahyd-rocarbonlead antiknock blend consisting essentially of a tetrahydrocarbonlead antiknock compound and a mixture of halohydrocarbon scavenging agents providing 0.1 to about 0.33 theory of fluorine, 0.3 to about 0.5 theory of bromine, and suificient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of 1, l,2,2- tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one halohydrocarbon in which each halogen has an atomic weight between 35 and 80 in an amount to provide all of said bromine and the rest of said chlorine.

2. A tetrahydrocarbonlead antiknock blend consisting essentially of a tetrahydrocarbonlead antiknock compound and a mixture of halohydrocarbon scavenging agents providing about 0.2 to about 0.33 theory of fluorine, about 0.5 theory of bromine, and suflicient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of l,1,2,2 tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one ethylene dihalide in which each halogen has an atomic weight between 35 and 80 in an amount to provide all of said bromine and the rest of said chlorine.

3. A tetraethyllead antiknock blend consisting essentially of tetraethyllead and a mixture of halohydrocarbon scavenging agents providing 0.1 to about 0.33 theory of fluorine, 0.3 to about 0.5 theory of bromine, and suflicient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of l,1,2,2-tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one halohydrocarbon in which each halogen has an atomic weight between 35 :and 80 in an amount to provide all of said bromine and the rest of said chlorine.

4. A tetraethyllead antiknock blend consisting essentially of tetraethyllead and a mixture of halohydrocarbon scavenging agents providing about 0.2 to about 0.33 theory of fluorine, about 0.5 theory of bromine, and sufficient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of 1,1,2,2-tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one ethylene dihalide in which each halogen has an atomic weight between 35 and 80 in an amount to provide all of said bromine and the rest of said chlorine.

5. A tetraethyllead antiknock blend consisting essentially of tetraethyllead ethylene dibromide in an amount to provide about 0.5 theory of bromine and 1,l,2,2-tetrachloro-l,2-difluoroethane in an amount to provide about 0.2 to about 0.33 theory of fluorine and about 0.4 to about 0.67 theory of chlorine.

6. A tetraethyllead antiknock blend consisting essentially of tetraethyllead, ethylene dibromide in an amount to provide about 0.5 theory of bromine and l,1,2,2-tetrachloro-l,Z-difluoroethane in an amount to provide about 0.33 theory of fluorine and about 0.67 theory of chlorine.

7. A tetraethyllead antiknock blend consisting essentially of tetraethyllead, ethylene dibromide in an amount to provide about 0.5 theory of bromine and l,l,2,2-tetrachlOrQ-LZ-difluoroethane in an amount to provide about 0.2 theory of fluorine and about 0.4 theory of chlorine.

8. A tetraethyllead antiknock blend consisting essentially of tetraethyllead and a mixture of halohydrocarbon scavenging agents providing a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of ethylene dibromide in an amount to provide 0.3 to about 0.5 theory of bromine, ethylene dichloride in an amount to provide about 0.4 to about 1.0 theory of chlorine, and 1,1,2,2-tetrachloro-1,2-difluoroethane in an amount to provide 0.1 to about 0.33 theory of fluorine and about 0.2 to about'0.67 theory of chlorine.

9. A fuel for Otto cycle engines which consists essentially a hydrocarbon fuel in the gasoline boiling range, 0.5 to 4 ml. of a tetrahydrocarbonlead antiknock compound per gallon of fuel and a mixture of halohydrocarbon scavenging agents providing 0.1 to about 0.33 theory of fluorine, 0.3 to about 0.5 theory of bromine, and sufficient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of l,l,2,2-tetrachloro-1,Z-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one halohydrocarbon in which each halogen has an atomic weight between 35 and in an amount to provide all of said bromine and the rest of said chlorine.

10. A fuel for Otto cycle engines which consists essentially a hydrocarbon fuel in the gasoline boiling range, 0.5 to 4 ml. of a lower tetraalkyllead antiknock compound per gallon of fuel and a mixture of halohydrocarbon scavenging agents providing about 0.2 to about 0.33 theory of fluorine, about 0.5 theory of bromine, and suflicient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of 1,1,2,2 tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one ethylene dihalide in which each halogen has an atomic weight between 35 and 80 in an amount to provide all of said bromine and the rest of said chlorine.

11. A fuel for Otto cycle engines which consists essentially a hydrocarbon fuel in the gasoline boiling range, 0.5 to 4 ml. of tetraethyllead per gallon of fuel and a mixture of halohydrocarbon scavenging agents providing 0.1 to about 0.33 theory of fluorine, 0.3 to about 0.5 theory of bromine, and sufficient chlorine to make a total of l to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of 1,1,2,2-tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one halohydrocarbon in which each halogen has an atomic weight between 35 and 80 in an amount to provide all of said bromine and the rest of said chlorine.

12. A fuel for Otto cycle engines which consists essentially a hydrocarbon fuel in the gasoline boiling range, 0.5 to 4 ml. of tetraethyllead per gallon of fuel and a mixture of halohydrocarbon scavenging agents providing about 0.2 to about 0.33 theory of fluorine, about 0.5 theory of bromine, and suificient chlorine to make a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of 1,l,2,2- tetrachloro-1,2-difluoroethane in an amount to provide all of said fluorine and at least part of said chlorine and at least one ethylene dihalide in which each halogen has an atomic weight between 35 and 80 in an amount to provide all of said bromine and the rest of said chlorine.

13. A fuel for Otto cycle engines which consists e'ssentially a hydrocarbon fuel in the gasoline boiling range,

about 3 to 4 ml. of tetraethyllead per gallon of fuel, ethylene dibromide in an amount to provide about 0.5 theory of bromine and 1,1,2,2-tetrachloro-1,Z-difluoroethane in an amount to provide about 0.2 to about 0.33 theory of fluorine and about 0.4 to about 0:67 theory of chlorine.

14. A fuel for Otto cycle engines which consists essentially a hydrocarbon fuel in the gasoline boiling range, about 3 to 4 ml. of tetraethyllead per gallon of fuel, ethylene dibromide in an amount to provide about 0.5 theory of bromine and 1,1,2,2-tetrachloro-1,2-difluoroethane in an amount to provide about 0.33 theory of fluorine and about 0.67 theory of chlorine.

15. A fuel for Otto cycle engines which consists es sentially a hydrocarbon fuel in the gasoline boiling range, about 3 to 4 ml. of tetraethyllead per gallon of fuel, ethylene dibromide in an amount to provide about 0.5 theory of bromine and l,1,2,2-tetrachloro-1,2-difluoroethane in an amount to provide about 0.2 theory of fluorine and about 0.4 theory of chlorine.

16. A fuel for Otto cycle engines which consists essentially a hydrocarbon fuel in the gasoline boiling range, about 3 to 4 ml. of tetraethyllead per gallon of fuel and a mixture of halohydrocarbon scavenging agents providing a total of 1 to about 2 theories of halogen, said mixture of halohydrocarbon scavenging agents consisting of ethylene dibromide in an amount .to provide about 0.5 theory of bromine, ethylene dichloride in an amount to provide about 0.4 to about 1.0 theory of chlorine, and l,1,2,2-tetrachloro-1,Z-difluoroethane in an amount to provide about 0.1 to about 0.33 theory of fluorine and about 0.2 to about 0.67 theory of chlorine.

References Cited in the file of this patent UNITED STATES PATENTS 2,398,281 Bartholomew Apr. 9, 1946 2,784,160 Blaker Mar. 5, 1957 2,822,252 Boag et a1. Feb. 4, 1958 2,869,993 Lyben Jan. 20, 1959 FOREIGN PATENTS 804,763 Great Britain Nov. 19, 1958 

9. A FUEL FOR OTTO CYCLE ENGINES WHICH CONSISTS ESSENTIALLY A HYDROCARBON FUEL IN THE GASOLINE BOILING RANGE, 0.5 TO 4 ML. OF A TETRAHYDROCARBONLEAD ANTIKNOCK COMPOUND PER GALLON OF FUEL AND A MIXTURE OF HALOHYDROCARBON SCAVENGING AGENTS PPROVIDING 0.1 TO ABOUT 0.33 THEORY OF FLUORINE, 0.3 TO ABOUT 0.5 THEORY OF BROMINE, AND SUFFICIENT CHLORINE TO MAKE A TOTAL OF 1 TO ABOUT 2 THEORIES OF HALOGEN, SAID MIXTURE OF HALOHYDROCARBON SCAVENGING AGENTS CONSISTING OF 1,1,2,2-TETRACHLORO-1,2-DIFLUOROETHANE IN AN AMOUNT TO PROVIDE ALL OF SAID FLUORINE AND AT LEAST PART OF SAID CHLORINE AND AT LEAST ONE HALOHYDROCARBON IN WHICH EACH HALOGEN HAS AN ATOMIC WEIGHT BETWEEN 35 AND 80 IN AN AMOUNT TO PROVIDE ALL OF SAID BROMINE AND THE REST OF SAID CHLORINE. 